Previous research suggests that it is profitable to attempt to describe the operations performed by visual neurons in terms of a transform of the visual image, and that a decomposition of visual response properties into component sinusoidal gratings is an apt transform to use. Quantitative studies of the properties of single neurons in the striate and extrastriate cortex of cats and monkeys will be undertaken to produce such a decomposition of their receptive fields, to analyze the neural mechanisms that lead to those properties. This analysis combined with neural unit data obtained from single units will permit a preliminary neural model of the cerebral cortex to be developed; this model will be used to attempt to explain certain properties of the human visual system, in particular its sensitivity to visual form and movement. Control of visual displays and data acquisition will be provided by digital computers, whose use permits the employment of a superior experimental design to reduce measurement problems due to fluctuations in response or sensitivity seen in units in these areas. The results of experiments performed on adult animals will be used as the basis for developmental studies of animals reared normally, or with partial or complete deprivation of pattern vision, using the same rigorous experimental methods. The results of these studies should reveal the importance and nature of innate and environmental contributions to normal development, and provide the basis for a model to explain the effects on human development of early visual experience and the sequelae of abnormal early experience. The results should thus provide information of both basic and applied value, both to the study of visual neural mechanism and to the analysis of neural development.